Hello everyone I have a 1989 Yamaha moto 4 250, I’ve tried starting it and it won’t turn over it’s only turned over for a seconds with starting fluid and now it won’t turn over, I’ve cleaned the carb it’s getting fuel I just did the valve adjustment. I’m thinking timing is off and I need help on how to set timing properly pls. It also backfires out the carb.

 

"Turn over" and "cranks" are the same thing so your post doesn't make sense. If it runs for a couple of seconds on starting fluid, that would indicate carb. However first things first. Change plug, check how good the spark is while doing so, see if it now starts. If not, re-set valve clearances, if they have closed up it will be bad to start. Next, clean out carb, remove float bowl and jets, blow them and the holes they came from out with compressed air. Check inlet manifold for cracks and put carb back. Try starting bike.

 

I cleaned the carb and did everything you told me it has a brand new spark plug and has good spark I just don’t know how to time and the timing was in fact off.

 

Timing shouldn't alter. If ignition timing is off, the flywheel key has sheared. Put piston at TDC by watching it through the plug hole while turning the crankshaft by hand. Check if the TDC mark on the flywheel agrees, this is visible through an inspection hole in the case, difficult to judge to within about 10 degrees, but flywheels usually slip a lot if the key lets go. If that is OK, check the TDC mark on flywheel agrees with the one on the cam sprocket. Can't remember how you get at it, but most Yams have a plate on the side of the head to cover the sprocket. If those marks agree, or the cam mark is exactly 180 degrees out, your valve timing is right. If not, the chain must have jumped, so will be slack. Most Yams have automatic adjusters, so you would need a new chain, as all the adjustment must have gone. However some early ones have manual adjusters. Best to get a workshop manual for setting it, if it is a manual adjuster type.